Device for measuring the geometry of a wheel axle of a motor vehicle

ABSTRACT

The invention relates to a device for measuring the geometry of a wheel axle of a motor vehicle, said device comprising a clamping chuck ( 56 ) which is provided with clamping jaws ( 32, 34, 36 ) and is used to receive a hub of a wheel axle, and a drive for rotating the clamping chuck ( 56 ). In order to increase the measuring precision, the drive is embodied as an electric drive, especially as a servomotor, and both rotatably drives the clamping chuck ( 56 ) and actuates the clamping jaws ( 32, 34, 36 ) of the clamping chuck ( 56 ) in the radial direction. Furthermore, according to the invention, the clamping jaws are radially displaced by means of a link motion with an eccentric plate or a spiral motion with a spiral of Archimedes in such a way as to obtain an automatic lock.

BACKGROUND OF THE INVENTION

DE 103 22 643.5 dated May 20, 2003

1. Field of the Invention

The present invention relates to a device for measuring the geometry ofa wheel axle of a motor vehicle by means of at least one, preferablythree, measuring sensors, the wheel axle comprising either a hub or ahub and a brake disk.

2. Description of the Prior Art

A device for measuring and adjusting the toe angle and/or camber of anaxle of a motor vehicle is known in which the hub of the axle isretained in a clamping chuck. Said clamping chuck is thereby mounted forrotation in a housing which is itself mounted so as to be pivotal abouta horizontal axis. The overall device in turn is float-mounted so thatthe device may be aligned three-dimensionally according to the actualtoe angle and/or camber of the axle to be measured. On the rear side ofthe clamping chuck there is provided an abutment surface against whichthe respective ones of the measuring sensors may abut in order tomeasure the geometry of the axle. It should be understood that such ameasurement always comprises a certain nonreproducible error since, dueto manufacturing tolerances, the surface of measurement is never capableof reproducing exactly the situation at the axle and above all since nonaccurate clamping of the hub in the clamping chuck also results inmeasurement errors.

BRIEF SUMMARY OF THE INVENTION

In view thereof, it is the object of the present invention to provide adevice for measuring the geometry of wheel axles by means of which thereal conditions at the hub and/or brake disk of the axle can be detectedmore accurately.

As a technical solution to this object the invention proposes to furtherdevelop the device mentioned herein above according to thecharacterizing portion of claim 1. Advantageous embodiments will appearfrom the subordinate claims.

A device configured in accordance with this technical teaching has theadvantage that utilizing an electric drive may allow for example thepneumatic drive known from EP 1 128 157 A1 to be eliminated. As aresult, the need for pneumatic air hoses and other component parts isalso obviated so that the entire device can be configured to be muchsmaller.

This advantage is even further reinforced in that the electric drive isdisposed axially centrally behind the clamping chuck and that from thereit acts onto the clamping chuck and the clamping jaws. As a result, thedrive is disposed outside of the critical zone so that the hub grippermay be configured to be commensurately small.

Another advantage is that it dispenses with the need to guide a fluidinto the rotating component parts so that rotary transmissionleadthroughs are no longer needed and that possible leakage and otherproblems are no longer allowed to occur.

Still another advantage is that one single electric drive permits bothto impart rotation to the clamping chuck and to actuate the clampingjaws. Thus, the entire hub gripper can be driven using but one singleelectric motor, which further contributes to reducing the overall size.

In a preferred embodiment, an electric coupling is utilized, saidcoupling switching between grasping and rotational movement and alsobeing actuated by the electric drive. This also contributes to reducingthe overall size.

In a particularly preferred embodiment, the clamping jaws are movedradially through a link motion control unit which in turn is actuatablethrough the electric drive. Utilizing this link motion control unitallows the clamping jaws to exert corresponding forces onto thecomponent part to be retained and a small and compact construction ofsame. It has been found advantageous to configure the link motioncontrol unit to be self-locking.

In another also preferred embodiment, the clamping jaws are caused tomove radially through a spiral motion control unit that is alsoactuatable via the electric drive. Utilizing said spiral motion controlunit permits guiding the clamping jaws with less friction so that theyare prevented from wedging. Another advantage is that the spiral motioncontrol unit allows the clamping jaws to cover a longer radial distance,thus allowing clamping of larger hubs. These advantages are reinforcedutilizing a spiral of Archimedes.

In another preferred embodiment, the measuring sensors are brought intodirect abutment with the hub or the brake disk. The advantage thereof isthat, in contrast to the state of the art, the sensors will not performindirect measurement but rather, in accordance with the invention,direct measurement. The advantage thereof is that by registering thedata directly at the hub and/or at the brake disk the geometric data canbe recorded without alteration, which leads to a much more preciseresult of the measurement.

The direct measurement of the wheel axle at its hub and/or brake diskfurther has the advantage that the values are measured directly at thewheel axle so that measurement errors as they may occur for example whenthe hub gripper is not coupled properly to the wheel axle are avoided.Further, possible measurement errors as they occur on component partsdue to manufacturing tolerances are avoided since no foreign componentsare involved in the measurement as the measurement is performed directlyat the wheel axle.

In an advantageous developed implementation, the measuring sensors aredisposed substantially beside the hub gripper. The advantage thereof isthat the sensors may thus be readily brought in proximity to therespective one of the measuring points on the hub or on the brake disk.

It has thereby been found advantageous to cause the sensors to bedisplaced in the longitudinal direction so that the hub gripper graspingand liberating the axle will not inadvertently damage the sensors.

Further advantages of the method of the invention, of the device of theinvention and of the hub gripper of the invention will become apparentin the appended drawings and in the following description of embodimentsthereof. Likewise, the invention lies in each and every novel feature orcombination of features mentioned above or described herein after. Theembodiments discussed herein are merely exemplary in nature and are notintended to limit the scope of the invention in any manner.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

In the drawing:

FIG. 1 is a schematic representation of the device of the invention in aperspective view;

FIG. 2 is an exploded illustration of the device in accordance with FIG.1;

FIG. 3 is a schematic, exploded view of a second embodiment of a deviceof the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the FIGS. 1 and 2 there is illustrated a device of the invention formeasuring the geometry of wheel axles of a motor vehicle, morespecifically for measuring the toe angle and/or camber. This deviceserves to automatically measure industrially manufactured wheel axles.This means that during series manufacturing of new wheel axles for motorvehicles the camber and toe angle of the wheels is only roughly presetduring assembly of the various component parts. For more precise settingof the camber and the toe angle, the wheel axle is positioned at adefined position on the assembly line and the device for measuring thegeometry of the wheel axle is fully automatically brought in proximityto the hub of the wheel axle. The toe angle and camber values arethereby advantageously obtained taking into consideration the wobblingof the hub or of the brake disk.

At need, a second device for measuring the geometry of the wheel axlecan be brought in proximity to the second wheel hub so that the twosides of the axle may be measured and set simultaneously.

The device for measuring the geometry of wheel axles of a motor vehicleillustrated in the FIGS. 1 and 2 includes a receptacle 10 that is floatmounted on a post (not shown) and is hinge-linked with a verticallyoriented pivot hinge 12 to a substantially U-shaped retaining arm 14. Ahub gripper 20 is attached to two legs 16, 18 of the retaining arm 14.In contrast to the vertically rotatable pivot hinge 12, the hub gripper20 is retained in the retaining arm 14 so as to be horizontallypivotable with a pivot axis 22 intersecting a longitudinal axis 24 ofthe hub gripper 20. The pivot axis 22 extends through the plane of theclamping jaws 32, 34, 36 in which the forces are introduced. Forces maythus be induced without torque.

The hub gripper 20 includes a body 26 that is pivotally attached to thelegs 16, 18 of the retaining arm 14 via supporting arms 28, 30. In thebody 26, three clamping jaws 32, 34, 36 are evenly spaced about thelongitudinal axis 24 and are carried so as to be radially displaceable.The clamping jaws 32, 34, 36 are thereby displaced radially through alink motion 38 so that they are allowed to grasp and retain the hub.

The link motion includes a guide disk 40 with three evenly spacedradially extending slots 42, 44, 46 and an eccentric plate 48 with threecurved long holes 50, 52, 54, said long holes 50, 52, 54 being disposedso that one end is relatively near the longitudinal axis 24 with thedistance from the longitudinal axis 24 increasing toward the other endof a respective one of the long holes. Put another way, the long holes50, 52, 54 are disposed eccentrically about the longitudinal axis 24 sothat self-locking is achieved in the clamping point.

As far as the link motion control unit 38 is concerned, a certain slot42, 44, 46 and a certain long hole 50, 52, 54 is associated with aclamping jaw 32, 34, 36 with each clamping jaw 32, 34, 36 extendingthrough the associated slot 42, 44, 46 into the corresponding long hole50, 52, 54 so that, when the eccentric plate 48 is caused to rotateaccordingly, the clamping jaws 32, 34, 36 are caused to moved evenlyradially outward or inward, thus being capable of grasping and retainingthe hub.

The link motion control unit 38, and the eccentric plate 48 inparticular, are driven by a servomotor that has not been illustrated infurther detail herein. The clamping chuck 56, including the clampingjaws 32, 34, 36 and the link motion control unit 38 are caused to rotateabout the longitudinal axis 24 by this servomotor, more specifically inorder to measure the wobble on the wheel axle. A switchable coupling(not shown), which is also driven by the servomotor, is provided betweenservomotor and clamping chuck 56.

The servomotor is capable of reproducing the momentary angular positionof the clamping chuck and, as a result thereof, also the momentaryadjusted position of the axle or of the hub so that possible unbalanceoccurring during wobble measurement can be accurately localized.

The link motion control unit 38 is designed to be self-locking in orderto prevent the clamping jaws 32, 34, 36 from being displaced. Utilizingthe link motion control unit 38 to actuate the clamping chuck 56 allowsmaking the hub gripper so small that the outer diameter of the body 26of the hub gripper 20 is smaller than the outer diameter of a hub of thewheel axle to be measured. As a result, the measuring sensors 58, 60, 62needed for measurement may be mounted beside the body 26 and may stilldirectly access the hub.

In a second embodiment illustrated in FIG. 3, the link motion of theclamping chuck is replaced by a spiral motion 70. The eccentric plate 72thereby comprises a groove 74 in the shape of a spiral of Archimedes,driver members attached to the rear side of the clamping jaws 76, 78, 80extending through the slots 42, 44, 46 of the guide disk 40 into thegroove 74 of the eccentric plate 72 so that the clamping jaws 76, 78, 80are radially displaced upon rotation of the eccentric plate 72. Itshould be understood that the driver members of the clamping jaws 76,78, 80 are thereby offset in such a manner that all the clamping jaws76, 78, 80 are always spaced the same distance from the longitudinalaxis 24 even if the discrete clamping jaws 76, 78, 80 engage thespiral-shaped groove 74 at different places.

The method for measuring the geometry of wheel axles of motor vehicleswill be explained herein after:

Once the industrially manufactured wheel axle has been brought to thestation for measurement, the hub gripper is roughly brought into theposition of the one wheel hub. The hub gripper 20 is thereby pivotalboth about a vertical and about a horizontal axis so that the hubgripper 20 is allowed to grasp the hub in such a manner that thelongitudinal axis 24 of the hub gripper 20 is aligned with the centralaxis of the hub. As soon as the hub gripper 20 has reached the desiredposition, the hub gripper 32, 34, 36 of the clamping chuck 56 isactuated. A coupling that has not been illustrated herein at first isswitched to bring the servomotor in direct contact with the clampingchuck 56, next the servomotor rotates the eccentric plate 48 so that theclamping jaws 32, 34, 36 are caused to move through the long holes 50,52, 54 and the slots 40, 42, 46 toward the longitudinal axis 24 and tograsp the hub. As the link motion control unit 38 is configured to beself-locking, the clamping jaws 32, 34, 36 now remain in their positionand reliably retain the hub of the wheel axle. Now, the coupling isswitched and the servomotor rotates the clamping chuck 56 about thelongitudinal axis 24, also causing thereby the hub to rotate. Now, themeasuring sensors 58, 60, 62 are deployed until they abut on the hub andare capable of measuring same. Measurement is performed taking therebythe wobble into consideration.

Once the measurement has been performed, the entire procedure isperformed in reverse and the clamping chuck is separated from the hub sothat the next wheel axle can be brought into position for measurement.

It should be understood that, depending on the application, a brake diskmay also be present on the wheel axle and that at need the measuringsensors may be brought in proximity to the brake disk in similar fashionin order to measure the wheel axle through the brake disk.

LIST OF NUMERALS

-   10 receptacle-   12 pivot hinge-   14 retaining arm-   16 leg-   18 leg-   20 hub gripper-   22 pivot axis-   24 longitudinal axis-   26 body-   28 supporting arm-   30 supporting arm-   32 clamping jaw-   34 clamping jaw-   36 clamping jaw-   38 link motion control unit-   40 guide disk-   42 slot-   44 slot-   46 slot-   48 eccentric plate-   50 long holes-   52 long holes-   54 long holes-   56 clamping chuck-   58 measuring sensor-   60 measuring sensor-   62 measuring sensor-   70 spiral motion control unit-   72 eccentric plate-   74 groove-   76 clamping jaw-   78 clamping jaw-   80 clamping jaw

1. A device for measuring the geometry of a wheel axle of a motorvehicle, with a clamping chuck (56) comprising clamping jaws (32, 34,36) for receiving a hub of the wheel axle, with a drive for rotating theclamping chuck (56), characterized in that the drive is configured to bean electric drive, more specifically a servomotor, and both rotatablydrives the clamping chuck (56) and actuates the clamping jaws (32, 34,36) of the clamping chuck (56) in the radial direction.
 2. The device asset forth in claim 1, characterized in that the electric drive isdisposed axially centrally behind the clamping chuck (56).
 3. A devicefor measuring the geometry of a wheel axle of a motor vehicle, with aclamping chuck (56) comprising clamping jaws (32, 34, 36, 76, 78, 80)for receiving a hub of the wheel axle, with a drive for rotating theclamping chuck (56), characterized in that the clamping jaws (32, 34,36, 76, 78, 80) are radially movable through a link motion control unit(38) or through a spiral motion control unit (70), with the link motioncontrol unit (38) and the spiral motion control unit (70) beingactuatable through an electric drive.
 4. The device as set forth inclaim 3, characterized in that the link motion control unit (38) or thespiral motion control unit (70) is self-locking.
 5. The device as setforth in claim 3, characterized in that the spiral motion control unit(70) comprises a spiral of Archimedes.
 6. The device as set forth inclaim 3, characterized by at least one, preferably three, measuringsensors (58, 60, 62), at least one measuring sensor (58, 60, 62) beingbrought into abutment with a brake disk and/or with the hub duringmeasurement.
 7. The device as set forth in claim 6, characterized inthat the at least one measuring sensor (58, 60, 62) is substantiallydisposed beside the hub gripper (20).
 8. The device as set forth inclaim 6, characterized in that the at least one measuring sensor (58,60, 62) is retained so as to be movable in the longitudinal direction.